A buffer is prepared by adding 24.6 mL of 0.65 M to 49.6 mL of 0.28 M. What is the pH of the final solution?

The given question is incomplete, the complete question is:

A buffer is prepared by adding 24.6 mL of 0.65 M NaF to 49.6 mL of 0.28 M HF. What is the pH of the final solution?

The correct answer is 3.23.

Explanation:

The calculations of pH in a buffer solution is determined with the help of Henderson-Hasselbalch equation, that is,

pH = pKa + log[conjugate base]/[acid]

= pKa + log[A⁻][HA]

Here Ka is the equilibrium constant.  

Based on the given information, the volume and concentration of NaF is 24.6 ml and 0.65 M. Now the millimoles of NaF can be determined by using the formula,  

millimoles = Molarity × Volume

= (0.65 M) (24.6 ml) (1 mmol/ml/1M)

= 16 mmol

Thus, the millimoles of NaF or F⁻ is 16 mmol.  

On the other hand, the volume and concentration given of HF is 49.6 ml and 0.28 M. Now the millimoles of HF will be,  

Millimoles = 0.28 M × 49.6 ml (1mmol/ml/1M)

Millimoles = 13.9 mmol

Thus, the millimoles of HF is 13.9 mmol.  

The value of Ka for strong acid is 6.8 × 10⁻⁴.  

Now the pH of the buffer solution can be determined by using the above mentioned Henderson-Hasselbalch equation,  

pH = pKa + log[F⁻]/[HF]

= -logKa + log[16 mmol]/[13.9 mmol]

= -log(6.8 × 10⁻⁴) + 0.06

= 3.17 + 0.06

= 3.23.  

Hence, the pH of the solution is 3.23.

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explanation:

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explanation:

metals have excess of electrons whereas non-metals have deficiency of electrons. thus, in order to gain stability metals easily donate their electrons to the non-metals.

for example, electronic configuration of sodium is and electronic configuration of phosphorous is .

when a phosphorous atom and sodium atom combine together then sodium will donate is extra one electron to the phosphorous atom. as a result there will be formation of ionic bond between sodium and phosphorous.

the reaction will be as follows.

there, are three sodium sodium atoms and each of them will donate its one extra electron to phosphorous atom. thus, the sub-shell of phosphorous gets completely filled.  

thus, we can conclude that electrons are transferred from atoms of sodium to atoms of phosphorous. this transfer makes the sodium atoms donate one electron and the phosphorous atoms to gain one electron. as a result, the sodium and phosphorus atoms strongly attract each other.